One hundred and six patients with operable breast cancer were studied at intervals one day before surgery, and at six weeks and one year post-operatively by means of taped clinical interviews and self-report questionnaires (Impact of Event Scale (IES) and General Health Questionnaire (GHQ-28)). A year after surgery, nine percent reported a high level of intrusive symptoms and 10% of avoidance symptoms compared to 18% and 14% after six weeks, respectively. Based on questionnaire data, a year after surgery, thirteen patients (12%) were estimated to have a posttraumatic stress disorder (PTSD) compared to fifteen patients (14%) after six weeks. Severity of posttraumatic stress symptoms (PTSS) after one year was significantly associated with impaired psychosocial functioning over the last year previous to surgery (p < 0.05), negative life events during the year before surgery (p < 0.05), health problems during the previous ten years (p < 0.01), and a personality trait characterized by high emotional reactivity (p < 0.001). Crisis support in the acute situation, type of surgery, axillary-node metastases, and postoperative adjuvant chemotherapy did not predict subsequent PTSS. Premorbid health variables, personality, and level of distress six weeks after surgery were most important risk factors for persistent PTSS in our patients with operable breast cancer stage I and II.